运行效果：

代码：

#include <QPdfWriter>
#include <QPainter>
#include <QDesktopServices>

void Widget::on_pushButton_5_clicked()
{
    //创建PDF文件
    QString file_path = QApplication::applicationDirPath() + "/text.pdf";

    QFile pdfFile(file_path);
    pdfFile.open(QIODevice::WriteOnly);
    QPdfWriter *pWriter = new QPdfWriter(&pdfFile);

    pWriter->setPageSize(QPagedPaintDevice::A4);
    pWriter->setResolution(300);
    pWriter->setPageMargins(QMarginsF(30, 30, 30, 30));

    QPainter *pPainter = new QPainter(pWriter);

    QFont font[5] = {QFont("宋体", 26, 60), QFont("宋体", 26, 61), QFont("宋体", 26, QFont::Normal), QFont("宋体", 26, QFont::Normal), QFont("宋体", 26, QFont::Normal)};
    font[0].setPixelSize(86);
    font[1].setPixelSize(61);
    font[2].setPixelSize(61);
    font[3].setPixelSize(42);
    font[4].setPixelSize(54);

    qDebug()<<pPainter->viewport().width()<<" "<<pPainter->viewport().height();

    int nPDFWidth = pPainter->viewport().width();
    int nPDFHeight = pPainter->viewport().height();

    //标题
    int y = 10;
    pPainter->setFont(font[0]);
    pPainter->drawText(QRect(0, y, nPDFWidth, 100), Qt::AlignCenter, QString("这是第一个PDF文档"));
    //画两条横线
    y += 140;
    pPainter->setPen(QPen(QBrush(QColor(0, 0, 0)), 5));
    pPainter->drawLine(0, y, nPDFWidth, y);
    pPainter->drawLine(0, y + 18, nPDFWidth, y + 18);
    //添加文字
    y += 60;
    pPainter->setFont(font[2]);
    pPainter->drawText(QRect(100, y, nPDFWidth/2, 70), Qt::AlignVCenter | Qt::AlignLeft, QString("器件型号: YT-CR810"));
    pPainter->setFont(font[2]);
    pPainter->drawText(QRect(nPDFWidth/2 + 100 , y, nPDFWidth/2 - 100, 70), Qt::AlignVCenter | Qt::AlignLeft, QString("器件编号: YT-CR810"));

    y += 90;
    pPainter->setFont(font[2]);
    pPainter->drawText(QRect(100, y, nPDFWidth/2, 70), Qt::AlignVCenter | Qt::AlignLeft, QString("装车车号: YT-CR810"));
    pPainter->setFont(font[2]);
    pPainter->drawText(QRect(nPDFWidth/2 + 100 , y, nPDFWidth/2 - 100, 70), Qt::AlignVCenter | Qt::AlignLeft, QString("实验日期: YT-CR810"));
    //小标题
    y += 110;
    pPainter->setFont(font[1]);
    pPainter->drawText(QRect(0, y, nPDFWidth, 80), Qt::AlignVCenter | Qt::AlignLeft, "减 振 器 标 准 参 数");
    //画表格
    y += 120;
    QStringList list;
    list<<"速度"<<"压力"<<"拉力"<<"阻尼系数"<<"不对称率"<<"正允差"<<"负允差";
    list<<"12.5m/s"<<"17KN"<<"15KN"<<"1.3kNs/m"<<"12%"<<"13%"<<"14%";
    pdfDrawForm(pPainter, y, 0, 2, 7, 100, font[3], list);

    y += 260;
    pPainter->setFont(font[1]);
    pPainter->drawText(QRect(0, y, nPDFWidth, 80), Qt::AlignVCenter | Qt::AlignLeft, "示功图");
    //插入图片
    y += 100;
    int imageBorder = 150;
    QPixmap pixmap = QPixmap::grabWidget(this, this->rect());
    float x = (float)(nPDFWidth - imageBorder * 2) / (float)pixmap.width();
    pixmap = pixmap.scaled(nPDFWidth - imageBorder * 2, x * pixmap.height(), Qt::IgnoreAspectRatio);
    pPainter->drawPixmap(imageBorder, y, pixmap);

    y += pixmap.height() + 90;
    pPainter->setFont(font[1]);
    pPainter->drawText(QRect(0, y, nPDFWidth, 80), Qt::AlignVCenter | Qt::AlignLeft, "减 震 器 测 试 结 果");

    y += 120;
    list.clear();
    list<<"拉伸行程"<<"0.00mm"<<"压缩行程"<<"0.00mm"<<"最大速度"<<"0.000m/s"<<"阻尼系数"<<"0.00kNs/m"
       <<"最大压力"<<"0.00kN"<<"压力偏差"<<"0.00%"<<"最大拉力"<<"0.00kN"<<"拉力偏差"<<"0.00%"
      <<"不对称率"<<"0.00%"<<"运动时间"<<"5S"<<"实验结果"<<"100%"<<"曲线结论"<<"100";
    pdfDrawForm(pPainter, y, 0, 3, 8, 100, font[3], list);

    pPainter->setFont(font[4]);
    pPainter->drawText(QRect(50, nPDFHeight, nPDFWidth/3, 80), Qt::AlignVCenter | Qt::AlignLeft, QString( "试验员: 张三"));
    pPainter->drawText(QRect(nPDFWidth/3+50, nPDFHeight, nPDFWidth/3, 80), Qt::AlignVCenter | Qt::AlignLeft, QString( "检查员签字: "));
    pPainter->drawText(QRect(nPDFWidth/3*2, nPDFHeight, nPDFWidth/3, 80), Qt::AlignVCenter | Qt::AlignLeft, QString( "签字日期: "));

    //绘制完毕
    delete pPainter;
    delete pWriter;
    pdfFile.close();

    //通过其他PDF阅读器来打开PDF
    QDesktopServices::openUrl(QUrl::fromLocalFile(file_path));
}

void Widget::pdfDrawForm(QPainter *paint, int y, int horzBorder, int row, int column, int unitHeight, QFont &font, QStringList &list)
{
    paint->setFont(font);

    paint->setPen(QPen(QBrush(QColor(0, 0, 0)), 2));

    int Width = paint->viewport().width() - horzBorder * 2;

    int unitWidth = Width / column;

    for(int i=0;i<row;i++) {
        int x = horzBorder;

        for(int j=0;j<column;j++) {
            paint->drawText(QRect(x, y, unitWidth, unitHeight), Qt::AlignCenter, list[i*column + j]);
            paint->drawRect(QRect(x, y, unitWidth, unitHeight));
            x += unitWidth;
        }

        y += unitHeight;
    }
}